News

Frequency Change for Canadian Time Transmission Station CHU

After 70 years of broadcasting Canada's official time, the National Research Council's shortwave station CHU will move the transmission frequency for the 7335 kHz transmitter to 7850 kHz. The change goes into effect at 0000 UTC on January 1, 2009.

Broadcasting 24 hours a day, CHU is a part of NRC's system for disseminating official time throughout Canada. Listeners hear tones to mark the seconds, a voice to announce the time in French and English and digital data to set computers. The atomic clocks at CHU are part of the ensemble of clocks in the time and frequency research laboratories at the National Research Council Canada in Ottawa. The NRC clocks are used in conjunction with clocks in the time laboratories of other countries to construct the internationally accepted scale of time, UTC (Coordinated Universal Time). Time transmissions on 3330 and 14670 kHz are not affected and will continue as before.

In April 2007, the ITU reallocated the 7300-7350 kHz band from a fixed service to a broadcasting service. Since then, the NRC said there has been a lot of interference on the 7335 kHz frequency from many information broadcasters around the world. "CHU listeners in Canada and around the world who have for so long considered the 7335 kHz frequency exclusively for time signals, are very vocal about this interference," said Raymond Pelletier, Technical Officer at the NRC-Institute for National Measurement Standards, who oversees the CHU facility. "We have heard from Amateur Radio operators, watchmakers, astronomers and navigators who use the tones and voice signals. We also received comments from those who use the carrier as a calibration source at a distance for their equipment. "

Pelletier noted that a leap second will be added at the end of December 2008; this will be indicated in the digital code until the time of the leap second. DUT1 will go from -0.6 to +0.4 seconds and will be indicated by double tones near the start of the minute and in the broadcast code.